A lift assembly of the type herein contemplated when associated with a vehicle, such as a van or mobile home, is usually mounted in a rear or side doorway thereof. It commonly comprises a platform which can be positioned on the exterior of the vehicle and level with the vehicle floor. The user wheels himself from the interior of the vehicle onto the platform and then actuates means to lower the platform to the ground level. The reverse sequence is followed when the user desires to return to the vehicle.
In the design of such lift assemblies, a number of characteristics are sought to be attained. For example, it is desirable to provide an assembly which is as compact as possible to permit the assembly to be permanently installed to either the interior or the exterior of the vehicle without unduly usurping interior space where space is a premium or creating an irregular external bulge which inhibits both the movement of the vehicle and the movement of other vehicles relative thereto.
Prior art assemblies frequently used hydraulic systems to raise and lower the platform but these systems were unacceptable because they were bulky and the hydraulic cylinders required an anchoring super structure as well as hydraulic reservoirs, pumps and the like.
Another prior art assembly employed a hydraulic platform which was strung on cables and pulleys and which folded into the vehicle (See: Fowler, U.S. Pat. Nos. 3,613,917 and 3,710,962) but again suffered from the area required by the assembly adjacent the vehicle in order to operate.
Still another hydraulic system was taught by Cassady in U.S. Pat. No. 3,893,576. Cassady suffered however from the use of a rotating platform which also required an extremely wide opening in the vehicle to function.
Other attempts were made to overcome certain of these defects and included a platform linked to a vehicle and extending from an upstanding stored position to a horizontal loading position level with the vehicle floor which was taught by Pohl in U.S. Pat. No. 3,984,014. A cable-and-drum combination was utilized to move the plaform between various horizontal positions.
Abreu, U.S. Pat. No. 4,026,387, attempted to solve the problem of storing the platform by folding it beneath the floor board of the trailer or vehicle when it was not in use but this suffered from the problem that the arrangement substantially reduced road clearance for the vehicle to which it was attached and was readily susceptible to damage and breakage while the vehicle was moving.
The most recent attempt to meet the need for an efficient and compact lifting assembly was disclosed by Collins et al in U.S. Pat. No. 4,113,121 in which the lift platform was further provided with a pin release to separate the lift platform from the lift frame when a failure of the primary power source occurs so the passenger could be freed.
While each of the foregoing prior art devices achieved some of the desired goals, each left serious deficiencies unfulfilled so that a great need still exists for a lift assembly which utilizes minimal space while having sufficient power to raise a load up to and lower such load from a vehicle doorway relative to the ground and is capable of operation by a disabled person to achieve untraumatic ingress to and egress from a vehicle.
Accordingly it is a primary object of the present invention to provide a new and improved lift assembly for use in conjunction with a vehicle which overcomes the deficiencies of the prior art devices.
It is another object of the present invention to provide a new and improved lift assembly in which a pivotable articulated platform receives vertical movement in response to the selective rotation of a threaded drive shaft within an integral collar member strategically linked to said platform.
These and still further objects as shall hereinafter appear are fulfilled in a remarkably unexpected fashion by the present invention as shall be readily discerned from a careful consideration of the following detailed description of an exemplary embodiment thereof, especially when considered in conjunction with the accompanying drawing which is hereinafter described.